Evolutionary Insights from Host-Parasite Interactions: Systematics, Population Genetics, and Coevolution
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Research in the Light lab is focused on the evolution, systematics, and population genetics of vertebrate and invertebrate taxa. I investigate cospeciation between mammals and their parasites to determine which factors are important in driving the association between distantly related taxa. Many parasites have complex ecological interactions with their hosts that persist over long evolutionary timescales. Parasites that are highly host specific tend to interact with their hosts in ways that facilitate a long-term coevolutionary history (i.e., cospeciation), whereas parasites that are not host specific may not cospeciate with their hosts. Comparisons of host and parasite phylogenies facilitate a greater understanding of how taxa have been associated through time. Although topological comparisons offer a variety of ways to investigate host-parasite associations, they cannot distinguish between trees that are concordant as a result of cospeciation and trees that are concordant for reasons unrelated to cospeciation (i.e., pseudocospeciation events such as sequential colonization). This level of discrimination requires use of a combination of methods that compare not only topological similarities between host and parasite trees, but also timing of putative codivergence events. I therefore supplement my studies with estimates of divergence times in host and parasite lineages because these analyses provide a way to distinguish between cospeciation and other processes that could result in identical branching patterns in host and parasite trees. Tests of cospeciation also offer the possibility for comparisons of rates of molecular evolution to determine if parasites are evolving faster, slower, or at the same rate as their hosts. Fundamental biological differences, such as differences in generation time, metabolic rate, DNA base composition, mitochondrial gene order, and evolution of parasitic lifestyle, have all been suggested as possible causes of rate differences between organisms. Therefore, studies incorporating multiple methodologies, such as phylogenetic comparisons, estimates of divergence times, and comparisons of molecular rates, have the potential to elucidate broad evolutionary processes operating in distantly related taxa.In my research, I hope to learn how hosts and parasites interact through time and how these interactions are affected by the population dynamics and other microevolutionary processes of the associated taxa. Understanding these interactions at the population level can potentially help me understand what effects natural history and ecology have on evolutionary processes such as coevolution. Past research in the lab has focused on multiple mammal-parasite assemblages (pocket gophers and chewing lice, heteromyid rodents and sucking lice, and a three-tiered assemblage of primates, sucking lice, and endosymbiotic bacteria). In general, research in the Light Lab relies on field work and Museum specimens, and I utilize molecular and morphological data from these recent and ancient specimens to help elucidate broad evolutionary processes operating in distantly related taxa.